1. Field of the Invention
The present invention relates to a gas generator having a thin-walled structure for an expandable air bag for protecting the occupant(s) of an automobile, and more particularly to an improvement in a housing of a gas generator suitably incorporated in a steering wheel to protect a driver of a passenger car when the collision of the car occurs.
2. Background of the Invention
As generally known, an air bag is a conventional safety device that is provided in a passenger car to protect a driver or passengers from an impact occurring when the car crashes. It comprises an air bag, and a gas generator for inflating the air bag in a very short period of time.
This gas generator has, as main constituent elements, a centrally positioned igniter in which a squib/enhancer is held, a cylindrical combustion chamber, formed so as to surround the igniter, housing gas generants therein, and a cross-sectionally rectangular filter/coolant chamber formed axially about the combustion chamber so that a gas generated in the combustion chamber passes through a filter and a coolant and flows through gas outlet ports formed in the side wall of the filter/coolant chamber and into an air bag.
Various types of structures of a housing for forming a combustion chamber and a filter/coolant chamber in such a gas generator have heretofore been proposed.
For example, Japanese Patent Publication-A No. 155857/1990 proposes a gas generator in which a combustion chamber is formed by a combination of a bottomed cylindrical portion of a housing body and a cover member welded to an opened part of this cylindrical portion so as to minimize the dimensions and weight of the gas generator.
Japanese Patent Publication-A No. 152639/1980 discloses a gas generator of a thin-walled structure formed so as to reduce the weight of a casing, in which a combustion chamber and a filter chamber are formed by a combination of a central cylinder in which an igniter is held, a cover, and an S-shaped casing. Outlet ports of the filter chamber (expansion chamber) being made in the form of slits by punching an extended portion of the casing.
However, when any of these conventional gas generators of a thin-walled structure are incorporated in a steering wheel of an automobile, safety problems arise since the wall of the housing which faces a driver consists of one thin plate covering a combustion chamber. Moreover, another disadvantage is that an assembly line for such gas generators, and the relative equipment used becomes complicated since the sealing of housings for the gas generants is done by welding.
An object of the present invention is to provide a gas generator of a weight-reduced, thin-walled structure having a housing of improved strength, capable of sealing gas generants by a non-welding method, which is advantageous with respect to the manufacturing equipment required.